R. to Castle Wolf. uses the Q3 engine, but its better. Q3 was fun, but that was a LONNnnnG time ago! But I remember when it first came out. I bought a new computer JUST to play it! Sooooo many hours wasted.
All-time best game though? Without a doubt: The Legend of Zelda. That's right. For the NES. I still play it on my computer. Best game EVER.